Axial displacement

Shafts, or other rotating machine components, are generally supported by a locating and a non-locating bearing (→ Bearing arrangements).

The bearing in the locating position must be able to locate the shaft axially in both directions. The most suitable bearings for the locating position are those bearings that can accommodate combined loads, or can provide axial guidance in combination with a second bearing.

Non-locating bearings must accommodate axial movement of the shaft, to avoid induced axial loads when, for example, thermal expansion of the shaft occurs. Bearings suitable for the non-locating position include needle roller bearings and NU and N design cylindrical roller bearings (fig. 1). NJ design cylindrical roller bearings and some full complement design cylindrical roller bearings can also be used.

All of these bearings accommodate axial displacement between the shaft and the housing, within the bearing. Values for the permissible axial displacement within the bearing are listed in the relevant product tables.

If non-separable bearings, e.g. deep groove ball bearings or spherical roller bearings (fig. 3) are used as non-locating bearings, either the inner or outer ring must have a loose fit so that it can slide on the shaft or in the housing (→ Radial location of bearings).